联合固氮40年: 从发现到应用
摘要
<sec><p indent="0mm">Biological nitrogen fixation (BNF), exclusively performed by prokaryotes, catalyzes the reduction of atmospheric dinitrogen to plant-available ammonium—a cornerstone process for sustainable agriculture by reducing synthetic fertilizer dependence, enhancing global food security, and mitigating environmental degradation. While rhizobia-legume symbiosis represents the most efficient BNF system, staple cereal crops (e.g., rice, wheat, maize) lack such symbiotic capabilities. Alternatively, associative diazotrophs colonize the rhizoplane, vascular tissues, and endophytic compartments of cereals and horticultural crops, deploying multidimensional plant-beneficial mechanisms: through nitrogen fixation, phytohormone secretion, antimicrobial compound synthesis, and enhanced host stress tolerance. To harness this potential, the Department of Microbiology at China Agricultural University has established a comprehensive “resource-to-application” research framework over four decades, integrating strain discovery, mechanistic dissection, synthetic biology engineering, and field deployment. </sec><sec> Systematic exploration has yielded transformative outcomes: isolation of >2,000 diazotrophic strains established the world’s largest germplasm repository, with 15 novel nitrogen-fixing species formally described. Mechanistic studies revealed an alanine dehydrogenase (ADH)-mediated coordination pathway in <italic>Paenibacillus</italic> that overcomes ammonium inhibition—a persistent bottleneck in non-legume BNF—whereby high ammonium induces ADH to deplete glutamine, mimicking low-nitrogen signaling to activate <italic>nif</italic> genes. In synthetic biology, co-expression of 15 nif genes in Saccharomyces cerevisiae achieved assembly of functional NifH and correctly structured NifDK tetramers (~240 kD), while chromosomal integration of 13 nif genes in rice (<italic>Oryza sativa</italic>) enabled stable NifDK assembly and protease-resistant NifH mutants (T17C,